Satellite surveys: a novel approach for assessing sea turtle nesting activity and distribution

Range of occurrence and abundance is a fundamental information that describes an animal population and is particularly important for species of conservation concern such as sea turtles. Although sea turtles lay clutches on land, which helps identifying breeding aggregations, the current knowledge on the distribution of these animals is far from being complete. Traditional ground surveys and more recent aerial surveys bear limitations due to logistic constraints, cost and safety concerns. We tested a novel approach based on high-resolution satellite imagery on a 12-km tract along the Atlantic coast of Florida (USA) by comparing counts from a satellite image with counts from traditional ground surveys. Daily track counts were underestimated in zones with higher human presence, probably due to tracks deleted or confounded by human activity, and overestimated in zones with lower human presence, probably due to persistence of old tracks. Results show that satellite surveys can provide the order of magnitude of nesting level in relatively undeveloped or low-frequented coastal tracts, which represent the main objective of any preliminary survey on sea turtle occurrence. Satellite imagery represents a new complementary tool available to conservationists for filling gaps about sea turtle occurrence, especially in remote or unsafe areas.